With the continuous progress of production technology, the display panel production line has been developed from the line of the first generation (in which the size of a glass substrate is 300 mm×400 mm) to the present line (in which the size of a glass substrate is 2850 mm×3050 mm). Since new products are continuously being developed and put into production, the difficulty in monitoring and managing products is exacerbated.
In order for a test device to detect the relative position of a particular display panel on a substrate, every display panel is designed with a test mark in the periphery of a display region. In order to increase the utilization rate of the glass substrate, the area of the display region is designed to be larger and larger. However, limited by the precision of an exposure device, some test marks need to be designed to be in a double exposure region. In general, in order to protect the photoresist at the position where the test marks in the double exposure region are located from being exposed out at the time of the second exposure, a protection mark of the same size as the test mark is further designed in the periphery of the display region.
The test mark and the protection mark may be formed together with the pattern of the display region by means of a patterning process. In conventional processes, the precision of placement of the exposure device was necessarily high. If there was a positional deviation between the first exposure and the second exposure of the substrate, it would result in the produced test mark falling outside the intended pattern outline size, and thereby failing to achieve the test purpose. As such, conventional processes not only proved unfavorable to monitoring of products, but also could result in large loss of product and investment.